import * as Cesium from '@cesium/Source/Cesium.js';

class SnowEffect {
  constructor(viewer, options) {
    if (!viewer) throw new Error('no viewer object!');
    options = options || {};
    this.snowSize = Cesium.defaultValue(options.snowSize, 0.02); //最好小于0.02
    this.snowSpeed = Cesium.defaultValue(options.snowSpeed, 60.0);
    this.viewer = viewer;
    this.init();
  }

  init() {
    this.viewer.scene.postProcessStages.remove(this.snowStage);
    this.snowStage&&this.snowStage.destroy();

    this.snowStage = new Cesium.PostProcessStage({
      name: 'czm_snow',
      fragmentShader: this.getFog_fs(),
      uniforms: {
        snowSize: () => {
          return this.snowSize;
        },
        snowSpeed: () => {
          return this.snowSpeed;
        }
      }
    });
    this.viewer.scene.postProcessStages.add(this.snowStage);
  }

  destroy() {
    if (!this.viewer || !this.snowStage) return;
    this.viewer.scene.postProcessStages.remove(this.snowStage);
    // this.snowStage.destroy();
    delete this.snowSize;
    delete this.snowSpeed;
  }

  show(visible) {
    this.snowStage.enabled = visible;
  }

  snow() {
    return "uniform sampler2D colorTexture;\n\
            varying vec2 v_textureCoordinates;\n\
            uniform float snowSpeed;\n\
            uniform float snowSize;\n\
            float snow(vec2 uv,float scale)\n\
            {\n\
                float time=czm_frameNumber/snowSpeed;\n\
                float w=smoothstep(1.,0.,-uv.y*(scale/10.));if(w<.1)return 0.;\n\
                uv+=time/scale;uv.y+=time*2./scale;uv.x+=sin(uv.y+time*.5)/scale;\n\
                uv*=scale;vec2 s=floor(uv),f=fract(uv),p;float k=3.,d;\n\
                p=.5+.35*sin(11.*fract(sin((s+p+scale)*mat2(7,3,6,5))*5.))-f;d=length(p);k=min(d,k);\n\
                k=smoothstep(0.,k,sin(f.x+f.y)*snowSize);\n\
                return k*w;\n\
            }\n\
            void main(void){\n\
                vec2 resolution=czm_viewport.zw;\n\
                vec2 uv=(gl_FragCoord.xy*2.-resolution.xy)/min(resolution.x,resolution.y);\n\
                vec3 finalColor=vec3(0);\n\
                //float c=smoothstep(1.,0.3,clamp(uv.y*.3+.8,0.,.75));\n\
                float c=0.;\n\
                c+=snow(uv,30.)*.0;\n\
                c+=snow(uv,20.)*.0;\n\
                c+=snow(uv,15.)*.0;\n\
                c+=snow(uv,10.);\n\
                c+=snow(uv,8.);\n\
                c+=snow(uv,6.);\n\
                c+=snow(uv,5.);\n\
                finalColor=(vec3(c));\n\
                gl_FragColor=mix(texture2D(colorTexture,v_textureCoordinates),vec4(finalColor,1),.5);\n\
            }";
  }

  //雪着色器
  getSnow_fs() {
    return 'uniform sampler2D colorTexture;\n' +
      'varying vec2 v_textureCoordinates;\n' +
      'float snow(vec2 uv,float scale)\n' +
      '{\n' +
      '    float time = czm_frameNumber / 60.0;\n' +
      '    float w=smoothstep(1.,0.,-uv.y*(scale/10.));if(w<.1)return 0.;\n' +
      '    uv+=time/scale;uv.y+=time*2./scale;uv.x+=sin(uv.y+time*.5)/scale;\n' +
      '    uv*=scale;vec2 s=floor(uv),f=fract(uv),p;float k=3.,d;\n' +
      '    p=.5+.35*sin(11.*fract(sin((s+p+scale)*mat2(7,3,6,5))*5.))-f;d=length(p);k=min(d,k);\n' +
      '    k=smoothstep(0.,k,sin(f.x+f.y)*0.01);\n' +
      '    return k*w;\n' +
      '}\n' +
      'void main(void){\n' +
      '     vec2 resolution = czm_viewport.zw;\n' +
      '     vec2 uv=(gl_FragCoord.xy*2.-resolution.xy)/min(resolution.x,resolution.y);\n' +
      '     vec3 finalColor=vec3(0);\n' +
      '     float c = 0.0;\n' +
      '     c+=snow(uv,30.)*.0;\n' +
      '     c+=snow(uv,20.)*.0;\n' +
      '     c+=snow(uv,15.)*.0;\n' +
      '     c+=snow(uv,10.);\n' +
      '     c+=snow(uv,8.);\n' +
      '     c+=snow(uv,6.);\n' +
      '     c+=snow(uv,5.);\n' +
      '     finalColor=(vec3(c));\n' +
      '     gl_FragColor = mix(texture2D(colorTexture, v_textureCoordinates), vec4(finalColor,1), 0.5);\n' +
      '}';
  }

  //雨着色器
  getRain_fs() {
    return 'uniform sampler2D colorTexture;\n' +
      'varying vec2 v_textureCoordinates;\n' +
      '	float hash(float x){\n' +
      '	     return fract(sin(x*133.3)*13.13);\n' +
      '	 }\n' +
      '	void main(void){\n' +
      '	     float time = czm_frameNumber / 600.0;\n' +
      '	     vec2 resolution = czm_viewport.zw; \n' +
      '	     vec2 uv=(gl_FragCoord.xy*2.-resolution.xy)/min(resolution.x,resolution.y);\n' +
      '	     vec3 c=vec3(.6,.7,.8); \n' +
      '	     float a=-.4;\n' +
      '	     float si=sin(a),co=cos(a);\n' +
      '	     uv*=mat2(co,-si,si,co);\n' +
      '	     uv*=length(uv+vec2(0,4.9))*.3+1.;\n' +
      '	     float v=1.-sin(hash(floor(uv.x*100.))*2.);\n' +
      '	     float b=clamp(abs(sin(20.*time*v+uv.y*(5./(2.+v))))-.95,0.,1.)*20.;\n' +
      '	     c*=v*b; \n' +
      '	     gl_FragColor = mix(texture2D(colorTexture, v_textureCoordinates), vec4(c,1), 0.5); \n' +
      '	}';
  }

  //雾气色器
  getFog_fs() {
    return 'uniform sampler2D colorTexture;\n' +
      '  uniform sampler2D depthTexture;\n' +
      '  varying vec2 v_textureCoordinates;\n' +
      '  void main(void)\n' +
      '  {\n' +
      '      vec4 origcolor=texture2D(colorTexture, v_textureCoordinates);\n' +
      '      vec4 fogcolor=vec4(0.8,0.8,0.8,0.5);\n' +
      '      float depth = czm_readDepth(depthTexture, v_textureCoordinates);\n' +
      '      vec4 depthcolor=texture2D(depthTexture, v_textureCoordinates);\n' +
      '      float f=(depthcolor.r-0.7)/0.2;\n' +
      '      if(f<0.0) f=0.0;\n' +
      '      else if(f>1.0) f=1.0;\n' +
      '      gl_FragColor = mix(origcolor,fogcolor,f);\n' +
      '   }';
  }
}

export default SnowEffect;
